using System;

namespace Org.BouncyCastle.Asn1
{
	/**
	 * Der BMPString object.
	 */
	public class DerBmpString
		: DerStringBase
	{
		private readonly string str;

		/**
		 * return a BMP string from the given object.
		 *
		 * @param obj the object we want converted.
		 * @exception ArgumentException if the object cannot be converted.
		 */
		public static DerBmpString GetInstance(
			object obj)
		{
			if (obj == null || obj is DerBmpString)
			{
				return (DerBmpString)obj;
			}

			throw new ArgumentException("illegal object in GetInstance: " + obj.GetType().Name);
		}

		/**
		 * return a BMP string from a tagged object.
		 *
		 * @param obj the tagged object holding the object we want
		 * @param explicitly true if the object is meant to be explicitly
		 *              tagged false otherwise.
		 * @exception ArgumentException if the tagged object cannot
		 *              be converted.
		 */
		public static DerBmpString GetInstance(
			Asn1TaggedObject	obj,
			bool				isExplicit)
		{
			Asn1Object o = obj.GetObject();

			if (isExplicit || o is DerBmpString)
			{
				return GetInstance(o);
			}

			return new DerBmpString(Asn1OctetString.GetInstance(o).GetOctets());
		}

		/**
		 * basic constructor - byte encoded string.
		 */
		public DerBmpString(
			byte[] str)
		{
			if (str == null)
				throw new ArgumentNullException("str");

			char[] cs = new char[str.Length / 2];

			for (int i = 0; i != cs.Length; i++)
			{
				cs[i] = (char)((str[2 * i] << 8) | (str[2 * i + 1] & 0xff));
			}

			this.str = new string(cs);
		}

		/**
		 * basic constructor
		 */
		public DerBmpString(
			string str)
		{
			if (str == null)
				throw new ArgumentNullException("str");

			this.str = str;
		}

		public override string GetString()
		{
			return str;
		}

		protected override bool Asn1Equals(
			Asn1Object asn1Object)
		{
			DerBmpString other = asn1Object as DerBmpString;

			if (other == null)
				return false;

			return this.str.Equals(other.str);
		}

		internal override void Encode(
			DerOutputStream derOut)
		{
			char[] c = str.ToCharArray();
			byte[] b = new byte[c.Length * 2];

			for (int i = 0; i != c.Length; i++)
			{
				b[2 * i] = (byte)(c[i] >> 8);
				b[2 * i + 1] = (byte)c[i];
			}

			derOut.WriteEncoded(Asn1Tags.BmpString, b);
		}
	}
}
